That's often the case with one of my friends who has a Gmail email address: anything that I send him (once or twice a year) doesn't even show up in his spam list without first making him start an email exchange to me => in my opinion that kind of filtering is just too easy to do (come on Google, at least put it into the spam folder and/or show it as a colored/blinking line and/or put some warnings whatever - don't just delete it), and of course it poses questions about oligopoly etc. How Gmail works is just not fair (in my opinion) :(((